1. Field of the Invention
The present invention relates to a liquid ejection head that ejects liquid and a method of manufacturing the same.
2. Description of the Related Art
A liquid ejection head for ejecting ink is generally mounted onto an ink jet recording apparatus for recording an image on a recording medium by ejecting the ink. As a mechanism for causing the liquid ejection head to eject ink, there is known a mechanism using a pressure chamber that is shrinkable in volume by a piezoelectric element. In this mechanism, the pressure chamber shrinks due to the deformation of the piezoelectric element to which a voltage is applied, and thus the ink inside the pressure chamber is ejected from an ejection orifice communicated to one end of the pressure chamber. As one liquid ejection head including such a mechanism, there is known a so-called shear mode type in which one or two inner wall surfaces of the pressure chamber are formed of the piezoelectric element, and the pressure chamber is caused to shrink by shear deformation of the piezoelectric element instead of extension or contraction deformation thereof.
Regarding ink jet apparatus for industrial applications or the like, there is a demand for use of high viscosity liquid. In order to eject high viscosity liquid, a large ejection force is required for the liquid ejection head. To satisfy this demand, there has been proposed a liquid ejection head called a Gould type, in which the pressure chamber is formed of a tubular piezoelectric member having a circular or rectangular sectional shape. In the Gould type liquid ejection head, the piezoelectric member extends or is deformed by contraction in the inward and outward directions (radial direction) about the center of the pressure chamber. In this manner, the pressure chamber expands or shrinks. In the Gould type liquid ejection head, the entire wall surface of the pressure chamber deforms, and this deformation contributes to the ink ejection force. Therefore, as compared to the shear mode type in which one or two wall surfaces are formed of the piezoelectric element, a larger ink jet force can be obtained. The method of manufacturing a Gould type liquid ejection head is disclosed in Japanese Patent Application Laid-Open No. 2007-168319.
In the manufacturing method disclosed in Japanese Patent Application Laid-Open No. 2007-168319, first, multiple grooves all extending in the same direction are formed in each of multiple piezoelectric plates. After that, the multiple piezoelectric plates are stacked so that the grooves are directed in the same direction, and are cut in a direction orthogonal to the direction of the grooves. The groove part of the cut piezoelectric plate forms an inner wall surface of the pressure chamber. After that, in order to separate the respective pressure chambers, the piezoelectric member present between the pressure chambers is removed to a certain depth. On upper and lower sides of the piezoelectric plate having the completed pressure chambers, a supply path plate and an ink pool plate, and a printed circuit board and an ejection orifice plate are respectively connected. In this manner, the liquid ejection head is completed. With this manufacturing method disclosed in Japanese Patent Application Laid-Open No. 2007-168319, the pressure chambers can be arranged in matrix, and hence the pressure chambers can be arranged in high density. Further, with this manufacturing method, because forming a groove in the piezoelectric plate is better in processing than opening a hole in the piezoelectric plate, the pressure chambers can be formed with high accuracy.
A technology of staggering multiple ejection orifices in a specific direction is known as a way to accomplish high-density recording with a liquid ejection head. In the liquid ejection head of Japanese Patent Application Laid-Open No. 2007-168319, however, the pressure chambers are arranged in two directions that intersect each other at right angles. If the technology is applied to this liquid ejection head, the liquid ejection head may not be able to eject ink from the ejection orifices because how the ejection orifices are arranged does not match how the pressure chambers are arranged.